More energy, same results: high energy settings do not improve the efficiency of dual energy lithotripsy during percutaneous nephrolithotomy

No prior in vivo clinical trial has investigated the effect of varying energy settings on the performance of a dual-energy lithotripsy. We prospectively evaluated various impact and frequency settings during PCNL procedures to achieve optimal fragmentation and extraction of large stones of varying density. Four impact and frequency settings were chosen based on a prior in vitro study and applied sequentially for 1 min each in a randomized manner during PCNL for large renal calculi greater than 3 cm in 24 patients: 4 Hz + 100% impact, 4 Hz + 30% impact, 12 Hz + 100% impact, and 12 Hz + 30% impact. Suction and ultrasonic settings were kept constant. For each setting, all removed fragments were collected, weighed, and dried to quantify stone removal rates. Fragments were categorized based on particle size, < 2 vs. ≥ 2 mm. Extraction rates (g/min), were expressed as medians and interquartile ranges (IQR). Statistical comparisons used the paired Wilcoxon Signed-Rank test. A sub-analysis was conducted based on density ( ≥ 1000 HU). 24 patients were enrolled. Median stone burden was 36 mm (IQR 32–54) and HU was 1170 (IQR 944–1336). Median extraction rates, 0.50 g/min (IQR 0.24–0.93), 0.55 g/min (IQR 0.22–0.87), 0.40 g/min (IQR 0.22–0.89), and 0.48 g/min (IQR 0.30–0.69), respectively, were not statistically different (Fig. 1a). Particle size was not influenced by impact and frequency settings (Fig. 1b). Fragmentation and extraction efficiency of highly dense stones (HU ≥ 1000) were not influenced by settings (Fig. 2). There was no significant difference in fragmentation or extraction efficiency based on stone composition (primarily calcium-based vs. non-calcium-based). Increased frequency and impact settings do not improve the efficiency of a dual-energy lithotripsy for clearance of large or hard stones and are unnecessary.